Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2011
Authors
Gry AlfredsenAbstract
Modified wood can provide protection against a range of wood deteriorating organisms. Several hypotheses have been put forward for the mode of action against wood decaying fungi, including inhibition of action of specific enzymes, but they still need further testing. This paper summarizes results from a project focusing on molecular studies of fungal colonization in modified wood. The focus has been on furfurylated wood, but also thermally modified and acetylated wood has been studied. Among the main finding was that wood modifications have an effect on the exploitation face of both brown and white rot colonization, but not on the exploration face. As already reported in a range of papers wood modification effects the wood moisture content, and this was confirmed within this project. New information was gathered about the effect on gene expression. Even before any mass loss was detected, differences in gene expression were measured. [...]
Abstract
Brown rot is the most common and destructive type of fungal decay for wood in service. These fungi depolymerize preferentially the structural carbohydrates, cellulose and hemicellulose in the cell wall leaving oxidized lignin behind. Modified wood can provide protection against a variety of wood deteriorating organisms, including decay fungi. However, there is still little known about the mode of function of the different wood modifications concerning the decay resistance. The biochemical mechanisms and gene products induced in brown rot during growth in modified wood are poorly understood. In this paper the data collected from mass loss studies and qPCR and qRT-PCR were used for profiling growth dynamics and gene expression of the brown rot fungus Postia placenta in different wood substrates through different stages of decay. Pinus sylvestris (L.) sapwood was used for the following treatments and modifications: chromated copper arsenate CCA (0.67%), furfurylation (WPG 37), thermal modification (D212) and acetylation (WPG 23). Untreated Pinus sylvestris (L.) sapwood was used as control. Samples were taken at different time intervals from 2 to 26 weeks. The highest mass loss and the highest fungal DNA content were found in the control samples while acetylated wood had the lowest mass loss and fungal DNA content. These results reflect a close relation of mass loss and fungal DNA content, both reflecting the amount of Postia placenta decaying the samples. Generally, expression of the investigated genes was highest in CCA treated wood. In the beginning of the incubation of all treated wood samples, the genes coding for oxidative metabolic activity had higher expression levels than the untreated control. In the end of the incubation most of these genes were less expressed than in the untreated control. The genes used for carbohydrate metabolism and the alcohol oxidase showed a significant decrease after 14 weeks of incubation. At the same time an increase in gene expression of an enzyme putative involved in lignin decomposition was detected.
Abstract
Some of the most common Norwegian wood species were tested in a Double layer test in South East Norway. After eight years of exposure the highest decay rating (≥3) was found in Scots pine sapwood, Norway spruce, alder, birch and aspen. Two wood types had decay rate ≤1: Scots pine heartwood and cedar. Wood moisture was logged and compared with precipitation during a two month period the second year of exposure. Scots pine sapwood had higher wood moisture content than Norway spruce, and a good correlation was found between precipitation and wood moisture content. When comparing similar materials exposed at three different geographical locations in Southern Norway, the samples exposed in Bergen had higher decay rating than samples exposed at Ås and Oslo.
Abstract
Moisture is often recognised as a key factor regarding the long time performance of wooden products, and one of the main challenges for timber products is to predict accurate service life in use class 3 (not covered above ground) and use class 4 (in soil or fresh water contact). A range of durability classification studies have been performed both in field and laboratory. But for several wood species information regarding the durability in use class 3 is lacking. Also, there is still a lack of studies comparing replicate wood products in different field exposure situations. This study evaluates the natural durability of different North European wood species in two different climates and in two different use classes. The wood species were compared with imported species and two preservative treatments. The overall picture shows a higher decay rating for wood species tested in ground contact compared with the results from the above ground “Double layer tests”. Moreover, the woods tested in Western Norway are more decayed than those tested in Eastern Norway. These findings can be explained by higher decay risk in use class 4 than in use class 3, and higher decay risk in a humid climate (Western Norway) than in a dry climate (Eastern Norway). The results indicate similar ranking of the durability of the wood species regardless of the environment they have been exposed to. The results from a linear regression show that MOE-loss of the mini-stakes after three years describes 70 % of the variation in decay rating of the “Double layer” stakes after six years exposure in Western Norway. This result strongly indicates that MOE-loss can be a prospective tool for rapid field testing of natural durability of wood.
Abstract
To understand the defence mechanisms utilized by decay fungi when exposed to different wood protection systems the study of gene expression can give us some answers. When the DNA sequences are known, primers can be designed to detect transcripts of genes with gene products related to basic cellular processes and hyphal growth. The characteristic gene products induced in different fungi by different wood protection systems can be identified. Studies on the expression of fungal genes will give us a better understanding of the fungal degradation of wood and we can optimize wood protection systems. Hence, no single technique will give us the answer to all questions about the decay of wood we need to gather small pieces of the puzzle using different approaches. The aim of the present study was to investigate the effects of acetylation level on the growth of Postia placenta with regard to amount of total DNA and gene expression targeting 7 different genes. This paper presents preliminary results after 4 weeks of incubation. The results presented in this paper are parts of a larger project which reaches over a period of 36 weeks with sampling times after 12, 20, 28 and 36 weeks. We found no mass loss in the acetylated samples after 4 weeks of incubation in a modified soil-block test. The presence of P. placenta DNA and the absence of mass loss could indicate on an inability of the mycelia to establish a wood exploitation phase. Two genes related to carbohydrate metabolism were expressed in a higher amount in P. placenta during growth on untreated wood than during growth on acetylated wood. However, for a third gene, also related to carbohydrate metabolism, the relationship was the opposite. Two genes related to oxidative metabolism were expressed in a higher amount in P. placenta during growth on acetylated wood than during growth on untreated wood and another two genes related to oxidative metabolism showed inconsistent results.
Abstract
Molecular methods are emerging also as useful tools for wood protection studies. The aim of the present study was to evaluate quantitative real-time polymerase chain reaction (qPCR) as a tool for investigating details of the colonization pattern of basidiomycete decay fungi in wood samples after 6 years of soil exposure. Samples of Pinus sylvestris L. (heartwood without treatment), furfurylated P. sylvestris sapwood and Cu-HDO treated P. sylvestris sapwood was in focus. The qPCR method based on basidiomycete DNA content in the wood had the highest sensitivity, while the ergosterol assay was more sensitive than the chitin assay. Visual rating was compared with laboratory analyses and was found to be correlating well with qPCR. This study demonstrates that qPCR in combination with microscopy provides relevant data about basidiomycete colonization in wooden material.
Abstract
Logging residues, branches and treetops after logging, were considered in the past as unsalable portions of the felled trees and remained on the landing. Currently, logging residues are harvested, stored in piles for variable time periods prior to being utilized as a bioenergy source. However, it is still unclear to what extent the colonization by decay fungi during outdoor storage impairs the fuel quality. Our objective was to find out whether the storage method influenced the amount of basidiomycetous fungi, the main wood degraders in logging residues....
Authors
Rastislav Solár Janka Dibdiakova Miroslav Mamo Frantiek Kaík Zuzana Rázgová Vladimír Vacek Jozef Sivák Milan GaffAbstract
A comparable series of specimens from spruce wood were pre-treated with sodium hydroxide, sodium hydroxide and hydrogen peroxide, or per-acetic acid sequences. The pre-treatments reduced the yield of pulps and their Kappa number noticeably, diminished the degree of polymerization moderately, and increased their brightness. One-step peroxide bleaching of pulps from the pre-treated spruce wood resulted in their higher brightness compared to bleached pulp from sound wood. From the viewpoint of improved properties of pulp, the most efficient were the sodium hydroxide/per-acetic acid and per-acetic acid/sodium hydroxide sequences. The pre-treatments did not influence mechanical strength of the obtained pulps significantly.
Abstract
This report presents presentations and summaries of posters presented during the conference "7th meeting of the Nordic-Baltic Network in Wood Materials & Engineering". The conference was held Oct. 27 to 28, 2011 in Oslo, and gathered around 70 participants from 9 countries. Norwegian Forest and Landscape institute hosted the event.